The I C-Bus Interface; Overview Of I C-Bus; Data Transfers; Start And Stop Of I C-Bus Communications - Epson RX8010SJ Applications Manual

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15. The I C-Bus Interface
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15.1. Overview of I C-Bus
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The I C-Bus supports bi-directional communications via two signal lines: the SDA (data) line and SCL (clock) line. A
combination of these two signals is used to transmit and receive communication start/stop signals, data transfer
signals, acknowledge signals, and so on.
Both the SCL and SDA signals are held at high level whenever communications are not being performed.
The starting and stopping of communications is controlled at the rising edge or falling edge of SDA while SCL is at
high level.

15.2. Data transfers

Data transfers are performed in 8-bit (1 byte) units once the START condition has occurred. There is no limit on
the amount (bytes) of data that are transferred between the START condition and STOP condition.
(However, the transfer time must be no longer than 0.95 seconds.)
15.3. Start and stop of I
START
condition
SCL
[ S ]
SDA
1) START condition, repeated START condition, and STOP condition
(1) START condition
• The SDA level changes from high to low while SCL is at high level.
(2) STOP condition
• This condition regulates how communications on the I
The SDA level changes from low to high while SCL is at high level.
(3) Repeated START condition (RESTART condition)
• In some cases, the START condition occurs between a previous START condition and the next STOP condition, in
which case the second START condition is distinguished as a RESTART condition. Since the required status is the
same as for the START condition, the SDA level changes from high to low while SCL is at high level.

15.4. Slave address

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The I C-Bus devices do not have any chip select or chip enable pins. All I
fixed unique number in it. The chip selection on the I
device send the required slave address to all devices on the I
interfacing, when the required slave address is agreed with its own slave address.
During in actual data transmission, the transmitted data contains the slave address and the data with R/W
(read/write) bit.
Slave address
bit 7 bit 6 bit 5
0 1 1
0 when write mode
RX8010SJ
ETM37E-07
2
C-Bus communications
Repeated START(RESTART)
condition
bit 4 bit 3 bit 2 bit 1
0 0 1 0
1 when read mode
Seiko Epson Corporation
[ Sr ]
s ( Max. )
0.95
2
C -Bus are terminated.
2
C-Bus is executed, when the interface starts, the master
2
C-Bus. The receiving device only reacts for
R/W
bit
bit 0
R/W
15. The I2C-Bus Interface
STOP
condition
[ P ]
2
C-Bus devices are memorized with a
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